Synthesis of 1, 7, 8, 9-Tetramethylphenanthrene

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Abstract

The characteristic alkaloids of the Erythrophleum genus are of interest for their cardiac activity and local anesthetic action. Cassaine, the major alkaloid of Erythrophleum Guineense, G. Don was isolated by Dalma. Cassaine (I) is an alkamine ester of cassaic acid (II). From a study of the degradation products, earlier investigators proposed structure (I) for cassaine and structure (II) for cassaic acid. In these suggested formulations for cassaine (I) and cassaic acid (II), the positions of the hydroxyl and the ketonic carbonyl groups are speculative and provisional. No chemical evidence for the location of the carbonyl and hydroxyl functions was advanced by any of the earlier investigators. Consequently, the problem of assigning exact positions to the hydroxyl and the ketone groups in the perhydrophenanthrene nucleus remained to be solved.
Sherman degraded cassaic acid to an aromatic hydrocarbon according to the sequence of steps mentioned below. Decarboxylation of cassaic acid (II) with quinoline followed by acetylation of the decarboxylated product furnished the compound (III). The carbonyl group of this compound {III) reacted with methyllithium to furnish the dihydroxycompound (IV) which was aromatized with selenium to an unknown aromatic hydrocarbon. If the ketonic function in cassaic acid were in position 9, as indicated in the formulation (II), the aromatic hydrocarbon derived from cassaic acid (II) by the above reactions should be 1, 7, 8, 9-tetramethylphenanthrene (V). As 1, 7, 8, 9-tetramethylphenanthrene (V) was unknown, this hydrocarbon had to be synthesized for the purpose of direct comparison with the degradation product from cassaic acid.
Mathieson of the University of London had also succeeded independently in degrading cassaic acid to a tetramethylphenanthrene. A direct comparison of the 1, 7, 8, 9-tetramethylphenanthrene (V) synthesized in this laboratory with that obtained by Mathieson showed the two hydrocarbons to be identical,
The assignment of position 9 to the carbonyl group of cassaic acid (II) based on this synthetic investigation has been corroborated by the independent investigations of Turner and his coworkers who synthesized the compound (XVIII) derived from cassaic acid. [TRUNCATED]

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Thesis (Ph.D)--Boston University

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